[LWM] feat(mobile): add stablecoins section to portfolio

[deepyjr]

✅ Checklist

• `npx changeset` was attached.
• Covered by automatic tests.
• Impact of the changes:
  • Portfolio screen: new stablecoins section rendering and asset display
  • Empty state and read-only mode of the portfolio
  • Navigation from stablecoin items to asset detail or market detail

📝 Description

The portfolio screen lacked a dedicated section for stablecoins, making it harder for users to track their stable assets at a glance.

This PR introduces a Stablecoins Section to the mobile Portfolio screen, mirroring the existing Cryptos section:

• Displays up to 6 stablecoins owned by the user
• When the user owns fewer than 2 stablecoins, the section is padded with popular defaults fetched from the DADA API (matching the desktop behaviour)
• Supports empty state and read-only modes (showing default stablecoins only)
• Tapping an asset navigates to the asset detail screen; tapping a placeholder navigates to its Market Detail page
• A "Show all" header button appears when more than 6 stablecoins are owned
• Analytics events (asset_clicked, button_clicked) are tracked on interactions

read only
https://github.com/user-attachments/assets/37972b96-afd5-4ae6-8387-568aed9a068e

no accounts

❓ Context

• JIRA or GitHub link: LIVE-26974

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🧐 Checklist for the PR Reviewers

• The code aligns with the requirements described in the linked JIRA or GitHub issue.
• The PR description clearly documents the changes made and explains any technical trade-offs or design decisions.
• There are no undocumented trade-offs, technical debt, or maintainability issues.
• The PR has been tested thoroughly, and any potential edge cases have been considered and handled.
• Any new dependencies have been justified and documented.
• Performance considerations have been taken into account. (changes have been profiled or benchmarked if necessary)

[github-actions]

Web Tools Build Status

Build	Status	Deployment
Web Tools Build	⏭️ Skipped	—
Native Storybook Build	⏭️ Skipped	—
React Storybook Build	⏭️ Skipped	—

[sonarqubecloud]

Quality Gate failed

Failed conditions
11.5% Duplication on New Code (required ≤ 3%)
4 New Code Smells (required ≤ 1)

See analysis details on SonarQube Cloud

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